MySQL query cache stats

Description

Admin dashboard widget measuring and monitoring MySQL / MariaDB query cache performance & statistics – to optimize sizing configuration and highlight bottlenecks.

Why

Database Query for Options Autoload is repeatedly executed for each WP page load and its poor performance has been identified as a good indicator for a poorly performing database resulting in slow site.

How

• Use dashboard widget to measure and monitor Options Autoload Query Time
• Use dashboard widget to measure and monitor Options Autoload Query Size
  This query result size increases constantly over time, as WP site usage grows – but its oversized sudden growth or constant balooning must not be overlooked.

Heavy plugins might rely heavily on adding data to Options Autoload Query Size.
Poorly written plugins causing WP performance degradation have been found to constantly increase this query result size.

Time Metrics

‘Options Autoload Query Time’ is measured in milliseconds (ms)

0 ms – great performance below one millisecond
1-2 ms – good performance
3-5 ms – OK performance
50+ ms – poor performance should be investigated

Size Metrics

‘Options Autoload Size’ is measured in Bytes
If you have the control to enable the database server wide query cache – configure query_cache_limit to be larger than Options Autoload Size

20,000 Bytes – freshly installed clean wordpress site
30,000 Bytes – small wordpress site
50,000 Bytes – medium wordpress site
250,000 Bytes – large wordpress site
2,000,000+ Bytes – too large should be investigated
( all above are rough metrics )